With increased global interconnectivity, reliance on e-commerce, network services, and Internet communication, computer security has become a necessity. Organizations must protect their systems from intrusion and computer-virus attacks. Such protection must detect anomalous patterns by exploiting known signatures while monitoring normal computer programs and network usage for abnormalities. Current antivirus and network intrusion detection (ID) solutions can become overwhelmed by the burden of capturing and classifying new viral stains and intrusion patterns. To overcome this problem, a self-adaptive distributed agent-based defense immune system based on biological strategies is developed within a hierarchical layered architecture. A prototype interactive system is designed, implemented in Java, and tested. The results validate the use of a distributed-agent biological-system approach toward the computer-security problems of virus elimination and ID.

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This paper provides a tutorial overview of the IRIDIUM@ low earth orbit (LEO) satellite system. Section I contains an introduction to the IRIDIUM@ network as well as the system specifications. Section II discusses the satellite constellation design, orbital parameters, and horizontal pointing angles between satellites. Section III introduces the idea of time dependent connectivity in a mobile network, and analyzes the cycle of network connectivity for IRIDIUM@. Section IV discusses the IRIDIUM@ Time Division Multiple Access (TDMA) and Frequency Division Multiple Access (FDMA) schemes and uses these to calculate the overall system capacity. Section V examines the call processing procedure to include user location and call set up. Finally, Section VI analyzes the network performance in terms of end-to-end delay and hop count.

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